An antenna transmits/receives an electromagnetic wave by outputting a beam. It is needed that direction of the beam, i.e. tilting angle is adjusted in various directions. Accordingly, the antenna employs a phase shifter of dividing a power and a tilting adjustment apparatus, etc. so as to adjust the tilting angle.
Hereinafter, structure of common antenna will be described with reference to accompanying drawing.
FIG. 1 is a view illustrating schematically a common antenna.
In FIG. 1, the antenna includes a reflection plate 100, a phase shifter 102, a tilting adjustment apparatus 104 and a shaft 106.
The phase shifter 102 is connected electrically to radiators, divides the power into the radiators, and is formed on the reflection plate 100.
The phase shifter 102 includes a dielectric substrate 110, a line 112, a central axis member 114, an arm member 116 and a rotation member 118.
The tilting adjustment apparatus 104 is connected to the rotation member 118 of the phase shifter 102 through the shaft 106, and provides rotatory power to the rotation member 118 through the shaft 106 to rotate the rotation member 118 during adjustment of the tilting angle. Accordingly, the central axis member 114 connected to a center of the rotation member 118 rotates in response to rotation of the rotation member 118, and the arm member 116 rotates in response to rotation of the central axis member 114. As a result, amount of the power fed to the radiators connected to both ends of the line 112 changes, and so the direction of the beam outputted from the radiators is changed.
Distance of the arm member 116 shifted while the tilting adjustment apparatus 104 rotates by one time (hereinafter, referred to as “tilting angle adjustment rate) is constant. That is, the tilting angle adjustment rate of the antenna is not changed.
In case that a user means to use the antenna as another usage, e.g. in another frequency band, the tilting angle adjustment rate of the antenna need to be changed from initial setting. However, since one antenna may not change the tilting angle adjustment rate, the tilting adjustment apparatus 104 or the phase shifter 102 should be exchanged or the antenna should be replaced with another antenna. As a result, utilization of the antenna is lowered and exchanging cost increases.